Occupant weight estimation systems are useful in connection with air bags and other pyrotechnically deployed restraints for purposes of discriminating the occupant category and judging whether, and how forcefully, to deploy the restraints. A well known weight estimation technique is to locate one or more fluid-filled bladders in or under a vehicle seat cushion, and to estimate the weight of the occupant based on a measure of the pressure in the bladder(s). See for example, the U.S. Pat. Nos. 5,987,370 and 6,246,936 to Murphy et al., and the U.S. Pat. Nos. 6,101,436 and 6,490,936 to Fortune et al., all of which are assigned to Delphi Technologies, Inc., as well as the U.S. Pat. No. 5,957,491 to Cech et al. and the U.S. Pat. No. 5,975,568 to Speckhart et al.
Typically, seat bladders are formed by peripherally joining two sheets of elastomeric material, by radio frequency welding, for example. Additional welds may also be formed at various locations within the periphery of the bladder in order to reduce fluid pooling and distention or bulging of the bladder due to localized loading, as well as to reduce the fluid volume, and therefore its weight. These inter-peripheral welds may be spot welds or seam welds, and can be used to form flow-through cells or fluid-free regions. See particularly the aforementioned U.S. Pat. Nos. 5,957,491; 5,975,568; 5,987,370; and 6,101,436.
A drawback of inter-peripheral welding in weight estimation seat bladders is that the bladder material in the vicinity of the weld provides a vertical support that effectively shunts a portion of the occupant weight through the bladder without significantly influencing the fluid pressure within the bladder. As a result, a given weight distributed over a relatively large area of the seat will produce a different pressure reading than the same weight when distributed over a relatively small area of the seat. Accordingly, what is needed is a bladder structure that will achieve the benefits of inter-peripheral welding without providing significant vertical support of occupant weight.